A critical consideration in the production of fluid hydrocarbons from marine deposits lies in providing a fluid communication system from the marine bottom to the surface after production has been established. Such a system, commonly called a production riser, ususally includes multiple conduits through which various produced fluids are transported to and from the surface, including oil and gas production lines, service, electrical and hydraulic control lines.
For offshore production, a floating facility can be used as a production and/or storage platform. Since the facility is constantly exposed to surface and sub-surface conditions, it undergoes a variety of movements. In such a zone of turbulence, heave, roll, pitch, drift, etc., may be caused by surface and near surface conditions. In order for a production riser system to function adequately with such a facility, it must be sufficiently compliant to compensate for such movements over long periods of operation without failure.
Examples of such compliant marine riser systems are disclosed and discussed in U.S. Pat. Nos. 4,182,584; 4,367,055; 4,400,109; and 4,423,984; and in paper OTC 4512, "Deepwater Production Riser", Panicker and Yancey, presented at the 15th annual Offshore Technology Conference, Houston, Tex., May 2-5, 1983. As seen from these references, a typical compliant riser system includes (1) a vertically rigid section which extends from the marine bottom to a fixed position below the zone of turbulence that exists near the surface of the water, and (2) a flexible section which is comprised of flexible flowlines that extend from the top of the rigid section, through the turbulent zone, to a floating vessel on the surface. A submerged buoy is attached to the top of the rigid section to maintain the rigid section in a substantially vertical position within the water.
Due to the water depths in those production areas where compliant riser systems are designed to be used, difficulties arise in securing the lower end of the rigid section to the marine bottom in that at the depths involved, any substantial use of divers in the installation is impractical, if not impossible. Further, the depths are such that the use of guidelines for installing the riser and/or lower components thereof is severely limited. Accordingly, the lower end of the rigid section must be capable of being remotely installed without any substantial assistance from divers or without the aid of guidelines to the surface.